1. Field of the Invention
The present invention relates to an abrasive for metal, a polishing composition for metal and a process for polishing a metal using the same. More precisely, the present invention relates to an abrasive and a polishing composition for polishing a metal film, particularly a copper-based metal film, to be used in the production of semiconductor devices, and a process for polishing a metal using said polishing composition for metal.
2. Description of Related Art
In recent years, various fine processing techniques have been researched and developed for advanced high integration and high performance of LSI wherein LSI stands for xe2x80x9cLarge Scale Integrationxe2x80x9d. Among them, the chemical mechanical polishing (hereafter, may be abbreviated as CMP) has been attracting the attention. CMP is a composite technique involving a chemical action and a mechanical action between a polishing composition and a material to be polished. It is an essential technique in the planarizing of insulating interlayers, particularly in the multilayer wiring formation step, in the metal plug formation, in the buried-type metal wiring formation and the like.
From the viewpoint of speeding-up of LSI, it is considered that the main current of metals used in the metal wiring in future would be a metal with a low resistance, and formation of the buried type wiring using a metal with a low resistance has been actively attempted. For example, various attempts have been made on copper-based metals as examples of metals with a low resistance.
For the polishing of copper-based metals, compositions containing, as the main ingredients, an abrasive of a particulate inorganic oxide such as alumina or silica and an oxidizing agent such as ferric nitrate or hydrogen peroxide have generally been used. There has been a problem, however, that copper-based metals could not be polished with a high speed using such a polishing composition containing an abrasive of inorganic oxide and an oxidizing agent.
In order to improve the polishing rate, therefore, a technology for high speed polishing with simultaneous etching have been developed by adding an additive with etching nature such as a complexing agent (for example, an amine, glycine or the like) capable of forming a water-soluble copper complex by reacting with copper ion. In this technology, however, there has been a tendency of generating the dishing, i.e. thinning in the central portion, in wide-spread regions of metal wiring film, particularly those buried in a groove or opening, by isotropic etching of metal when a metal wiring formed on a semiconductor substrate is polished with a polishing composition containing an additive with etching nature. When dishing occurs, problems arise that, in addition to deterioration of the planarity, high resistance as compared with a layer of buried metal wiring, and some others, will result.
On the other hand, attempts have also been made to accomplish polishing, without etching, by polishing a copper complex, which is difficultly soluble in water and more mechanically fragile than copper, formed on the surface of copper by reaction of copper.
However, while the polishing composition forming a fragile copper complex allowed a faster polishing as compared with the above-described conventional polishing composition containing an inorganic oxide particle and an oxidizing agent, it had a problem that its polishing rate was slower than that with the above-cited polishing composition with etching nature.
In addition, since copper-based metals has a low hardness, problems occurred that the surface of the copper-based metal became rough by scratches and that abrasives were embedded in the metal when particles of inorganic oxide having a high hardness were used as the abrasives.
Therefore, a method in which particle containing a soft organic polymer compound as the main component has been proposed. This method had also a problem that a high polishing rate could not be obtained unless it contained an additive with etching nature.
The object of the invention is to provide an abrasive for metal which allows a high speed polishing of metals, which inhibits generation of scratches on the polishing surface and which inhibits etching of the metal; an abrasive for metal which allows formation of excellent processing surface. Another object of the invention is to provide a polishing composition for metal which enables further improvement in planarity of polishing surface.
As the result of extensive studies conducted for solving the above-described problems, the present inventors have found the fact that the above objects can be attained by using particle having a functional group capable of trapping a metal ion and thus completed the invention.
The invention relates to [1] an abrasive for metal comprising particle having a functional group capable of trapping a metal ion.
The present invention also relates to [2] a polishing composition for metal comprising an abrasive for metal according to the above described [1], an oxidizing agent and water.
Further, the present invention relates to [3] the polishing composition for metal according to the above described [2] further comprising at least one selected from the group consisting of a spherical particle, benzotriazole and a benzotriazole derivative.
Still further, the present invention relates to [4] a process for polishing a metal by chemical mechanical polishing, said process using a polishing composition for metal according to the above described [2] or [3].